Process of manufacturing available phosphoric acid.



JAMES H. CONNOR, OIE NASHVILLE, TENNESSEE.

PROCESS OF MANUFACTURING AVAILABLE PHOSPHORIC ACID.

rote-too.

No Drawing.

Specification of Letters Patent.

Patent-ed oer. so, rare.

Application filed October 21, 1911. Serial No. 655.962.

other phosphatic material, for the purpose o converting the insoluble phosphates contained therein into soluble phosphates and thereby making the same available as fertilizers.

The invention particularly applicable to the treatment of phosphate rock and other phosphatic materials which contain a as sandy matter or dirt and which for that reason have heretofore been unmarketable and unsalable. The invention, however, is applicable to the treatment of phosphatic umtcrials of any kind.

The object of the invention is to provide for the treatment of such phosphatic materials, and particularly low-grade phosphate rocks and pebbles in a manner to convert the insoluble phosphates therein into soluble and therefore availablephosphoric acid, without the use of sulfuric acid, and at a comparatively low cost.

In carrying out the process the phosphate rock or other phosphaticmaterial as it comes out of the ground and while in its CL adestate, and without washing or cleaning, is first dried and then ground, crushed or pulverized to such size that all portions thereof will be acted upon in the subsequent treatment thereof. The size to which it is reduced may vary, but it has been found that a size such as to pass through a sieve of 60 meshes tothe inch gives excellent results. The ground, crushed or pulverized phosphatic material is then mixed with suitable quantities of lime stone and soda. The

. limestone is also ground, crushed or pulverized to substantially the same degree of fineness the phosphatic material. or finer, from to 100 mesh. Any form of soda may be used. some form of sodium carbonate. preferably the ordinary commercial soda ash. Soda ash is preferred onv account "first, of its relatively low cost and second because it converts a large pcrcentageof.

the phosphoric acid into "citrate soluble form. By ,using what is connnercially known as sulfur soda ash, which contains sulfur as an impurity and is even cheaper than ordinary soda ash, the percentage of phosphoric acid rendered available is not only very high but is largely water soluble. The proportion of soda added to the crushed phosphatic material depends upon the character of the phosphatic 'material and the quantity of phosphates contained therein which are to be rendered available. The proportion of limestone which is added varies with the percentage of sand or silica and iron contained in the crushed phosphatic material; The limestone serves largely as a flux for the silica and iron so as to give freer action to the soda. Hence the greater the percentage of silica and iron the larger will be the amount of limestone which is added. Good commercialresults have been obtained by usin from 250 to 400 pounds of soda ash and to 100 pounds of limestone for each H0O pounds of-phosphatic material. The mixture is then subjected to a comparatively high temperature for from about forty minutes to one hour. the temperature varying from 2000 to 3000 degrees l ahrenheit. Any form offurnacc or kiln may be used for roasting the material, but it is preferred to use an ordinary rotary kiln on account of being thereby enabled to maintain a steady and uniform heat, and also because the action of the kiln keeps the material in fairly small lumps or globules, thereby insuring the thorough roasting of the mass throughout.

If it is desired that a portion of the phosphoric acid be water soluble there added to the mixture prior to calcining a quantity of either oxid of iron or sodium sulfate. preferably tine dust which is largely a red oxid of iron. From 25 to '50 pounds of flue dust for each H0O pounds of phosphatic material is sufficient. The flue-dust causes the mixture to fuse very rapidly and produce an energetic reaction which results in rendering a portion ofthe phosphoric acid water soluble.

The mixture can be blown into-the kiln in a dry form, but preferably it is treated in a wet state by adding water thereto in slithcient quantities to convert the mixture to the consistency of thick mud, the ingredients being thoroughly mixed after the water is zation of the sodium component.

same time the action of the rotary kiln small size so that the entire mass added to convert the same into a uniform mass of substantially the consistency stated. This not only insures a thorough intermingling or more uniform mixture or distribution of the soda with the phosphatic matter than if the materials were merely mixed in dry condition, but also results in the dissolved sodium carbonate soaking into or penetrating the particles of crushed phosphatic material, as a result of which the action of the re-agent is not only rendered more rapid but also produces a larger percentage of phosphoric acid.

In the treatment of the wet mass in the kiln the wet material does not immediately disintegrate but remains in masses of greater or less size. This has-a tendency to hold the available elements, such as the carbon monoxid and the carbon dioxid in themass and prevents their too rapid escape and therefore insures the thorough action of the sodium carbonate onuthe phosphates and particularly prevents the excessive volatili- At the breaks the mass into lumps of sutiiciently is thoroughly roasted.

Limestone is preferred over burnt lime, as in the heat of the kiln it converted into quick lime which in this nascent state acts more energetically on the silica and iron. Furtherfore the carbonic gas liberated in the burning of the limestone supplements the carbonic gases of the soda in its action on the phosphates.

.The application of a heat of the temperature specified and continued for substantially the time specified results in separating the phosphoric acid and rendering the same soluble and available. The result is a rather concentrated product very rich in available phosphoric acid. which .is sutiiciently separate and soluble to render the product available as afertilizer.

The roasted mass comes out of the kiln in the form of small lumps somewhat resembling clinker. This is then ground, crushed or pulverized to such fineness as is desirable for fertilizing purposes, preferably to an impalpable powder or flour, and is then packed and ready for market without further treatment.

By means of the process described it is possible to form a high grade fertilizer, rich in available phosphoric acid, from cheap phosphatic, rock, earth, pebbles and the like, which is found in large quantities in various parts of the country, mixed with various impurities, such as alkali earths, but which have not heretofore been available for fertilizing purposes on account of the cost of known processes for treating the same to render the phosphoric acir available. and which processes although ea sive resulted in producing only a very indifferent fertilizer from such impure phosphate rocks and the like.

lVhat I claim is:

' l. The method of treating phosphatic material to render the insoluble phosphates available, consisting in reducing phosphatic material to substantially a size to pass through a screen of sixty meshes to the inch, then adding-thereto sodium carbonate and crushed limestone, the tpiantity of sodium carbonate being at least double that of the" limestone, and subjecting the mixture to a temperature of from 2000 to 3000 degrees Fahrenheit for such length of time that the phosphoric acid becomes soluble.

2. The method of treating phosphatic material in order to render the insoluble phosphates available, consisting in reducing the phosphatic material to substantially a size to pass through a screen of sixty meshes to the inch, then adding thereto sodium oarbonate and crushedihme in proportions of approximately 250 to 400 pounds of sodium carbonate and 50 to 100 pounds-of pulverized limestone to each 1400 pounds of phosphatic material, and then fusing the same for such length of time that the phosphoric acid becomes soluble.

3. The method of treating phosphatic material in order to render the insoluble phosphates available, consisting in reducing the phosphatic material to substantially a size to pass through a screen of sixty meshes to the inch, then adding thereto sodium carbonate and crushed limestone in the pro portions of substantially 250 to 400 pounds of sodium carbonate and 50 toll00 pounds of pulverized limestone to each 1400 pounds of phosphat-ic material, and then subjecting the same to a temperature of from 2000 to 3000 degrees Fahrenheit for a period of forty minutes to one hour.

4. The method of treating phosphatic material in order to render the insoluble phosphates available, consistin in reducing the phosphatic material to substantially a size to pass through a screen of sixty meshes to the inch, then adding thereto sulfur soda ash and crushed limestone and subjecting the same to.a temperature of from 2000 to 3000 degrees Fahrenheit for such length of terial in order to render the insoluble phos- The method of treating phos hatic ma Ill phates available, consisting in grinding the time that the phosphoric acid becomes 10 phosphatic material, then adding thereto soluble. a

soda ash, crushed limestone and iron oxid In testimony whereof, I have hereunto set in proportions of approximately 250 to 400 my hand.

= pounds of soda ash 50 to 100 pounds of I crushed limestone, aiid 25 to 50 pounds of JAMES CONNOR" iron oxid to each 1400 ounds of phosphatie Witnesses: material, and then su jectingthe mixture F. W. VVINCL' R, to such temperature and for such length of MARY E. CA HOON. 

